Allyl isomerization mediated by cyclopentadienyl group 6 metal compounds

Article abstract of DOI:10.1021/om700293a

Reactions at mild temperatures of the acetonitrile adducts [M(CO) ₃(NCMe)₃] (M = Mo (1), W (2)) with various substituted cyclopentadienes in THF give the hydrido derivatives [MH{η⁵- C₅R₄Si(CH₃)₂-(CH₂CH= CH₂)}(CO)₃] (M = Mo, R = H (5a), R = CH₃ (6), M = W, R = H (7a), R = CH₃ (8a)) and [MoH{η⁵-C ₅R₄R′}(CO)₃] (R = CH₃, R′ = H (16); R = H, R′ = SiMe₃ (17)) in isolated yields of 60-70%. THF solutions of derivatives 5a, 7a, and 8a undergo isomerization of the cyclopentadienyl-tethered-allyl unit to give the corresponding methyl-vinyl-dimethylsilyl-η⁵-cyclopentadienyl hydrido compounds [MH{η⁵-C₅R₄Si(CH_{3 2}(CH=CHCH₃)}(CO)₃] (M = Mo, R = H (5b), M = W, R = H (7b), R = CH₃ (8b)) in final a:b ratios of ca. 2:1, 2:1, and 1:1, respectively. Solvent polarity seems to be crucial in these transformations. Dehydrogenation and desilylation of 5a in THF solutions to give the dinuclear derivative [Mo{η⁵-C₅H ₄Si(CH₃)₂(CH₂CH=CH₂) }(CO)₃]₂ (9) and [MoH(η⁵-C ₅H₅)(CO)₃] (15), respectively, are processes competitive with the allyl isomerization. Treatment of 5a and 7a with equimolar amounts of ONMe₃ permits isolation of pure compound 9 and [W{η⁵-C₅H₄Si(CH₃) ₂(CH₂CH=CH₂)}(CO)₃]₂ (10) in isolated yields of 80-90%. Coordination of the olefin pendant unit to the metal was detectable only by reaction of 5a and 7a with [CPh₃] [B(C₆F₅)₄] to give the cationic species [M{η⁵-C₅H₄Si(CH₃) ₂(CH₂CH=CH₂)}(CO)₃][B(C ₆F₅)₄] (M = Mo (18), W (19)). Molecular structure determinations by X-ray diffraction methods for derivatives 8a and 9 are also reported.

Full text of DOI:10.1021/om700293a

Organometallics 2007, 26, 3831-3839
3831
Allyl Isomerization Mediated by Cyclopentadienyl Group 6 Metal
Compounds
Eva Royo,* Sergio Acebro´n, Marta Elena Gonza´lez Mosquera, and Pascual Royo*
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, UniVersidad de Alcala´,
28871 Alcala´ de Henares, Madrid, Spain
ReceiVed March 27, 2007
Reactions at mild temperatures of the acetonitrile adducts [M(CO)3(NCMe)3] (M ) Mo (1), W (2))
with various substituted cyclopentadienes in THF give the hydrido derivatives [MH{η5-C5R4Si(CH3)2-
(CH2CHdCH2)}(CO)3] (M ) Mo, R ) H (5a), R ) CH3 (6), M ) W, R ) H (7a), R ) CH3 (8a)) and
[MoH{η5-C5R4R′}(CO)3] (R ) CH3, R′ ) H (16); R ) H, R′ ) SiMe3 (17)) in isolated yields of
60-70%. THF solutions of derivatives 5a, 7a, and 8a undergo isomerization of the cyclopentadienyl-
tethered-allyl unit to give the corresponding methyl-vinyl-dimethylsilyl-η5-cyclopentadienyl hydrido
compounds [MH{η5-C5R4Si(CH3)2(CHdCHCH3)}(CO)3] (M ) Mo, R ) H (5b), M ) W, R ) H (7b),
R ) CH3 (8b)) in final a:b ratios of ca. 2:1, 2:1, and 1:1, respectively. Solvent polarity seems to be
crucial in these transformations. Dehydrogenation and desilylation of 5a in THF solutions to give the
dinuclear derivative [Mo{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]2 (9) and [MoH(η5-C5H5)(CO)3] (15),
respectively, are processes competitive with the allyl isomerization. Treatment of 5a and 7a with equimolar
amounts of ONMe3 permits isolation of pure compound 9 and [W{η5-C5H4Si(CH3)2(CH2CHdCH2)}-
(CO)3]2 (10) in isolated yields of 80-90%. Coordination of the olefin pendant unit to the metal was de-
tectable only by reaction of 5a and 7a with [CPh3][B(C6F5)4] to give the cationic species [M{η5-C5H4Si-
(CH3)2(CH2CHdCH2)}(CO)3][B(C6F5)4] (M ) Mo (18), W (19)). Molecular structure determinations by
X-ray diffraction methods for derivatives 8a and 9 are also reported.
to the metallic center.5 Furthermore, the chelating effect of allyl
systems tethered to chelating P, N, or S atoms has already been
shown to stabilize the otherwise labile π-alkene early transition
metal bonds.6,7 These reasons moved us to undertake similar
studies using the allyl-dimethylsilyl-η5-cyclopentadienyl ligand
with more electron-rich group 6 metal complexes.
Transition metal hydrides are of fundamental importance in
organometallic chemistry, particularly due to their involvement
as catalysts or proposed intermediates in a wide variety of
processes.8 The hydrido tricarbonyl η5-cyclopentadienyl mo-
lybdenum and tungsten compounds have been extensively
studied and used as convenient precursors for several synthetic
Introduction
Cyclopentadienyls have been among the most important
ligands in organo-transition metal chemistry, as they form a wide
range of derivatives whose steric and electronic properties can
be easily tailored by varying the ring substituents. This versatility
of cyclopentadienyl units can be further enhanced when their
substituents bear functionalized side chains, which can act as
potential coordinating groups. These variations on the cyclo-
pentadienyl unit open access to ligand architectures with a
hemilabile binding profile, which can stabilize otherwise
unstable organometallic catalytic intermediates. Other interesting
properties that these ligands impart to their metal species include
higher catalytic reactivity, introduction of chirality, changing
solubility properties, and the possibility to act as anchoring
moieties to develop new supported single-site catalysts.1 Within
this context, pendant double bonds attached to cyclopentadienyl
rings have already been shown to influence properties of olefin
polymerization catalysts generated therefrom.2 In previous
works, we reported the synthesis and chemical behavior of
various allyl-dimethylsilyl-η5-cyclopentadienyl metallocene-type
group 4 and 5 metal compounds.3 Compared to similar alkyl
pendant chains,2a-c,4 the higher acidity and fluxional character
of the silyl substituents could favor coordination of the alkene
(3) (a) Ramos, C.; Royo, P.; Lanfranchi, M. Organometallics 2007, 26,
445. (b) Ramos, C.; Royo, P.; Lanfranchi, M. Eur. J. Inorg. Chem. 2005,
19, 3962. (c) Martinez, G.; Royo, P. Organometallics 2005, 24, 4782. (d)
Nicola´s, P.; Royo, P.; Galakhov, M. V.; Blacque, O.; Jacobsen, H.; Berke,
H. Dalton Trans. 2004, 2943, and references therein. (e) Cano, J.; Gomez-
Sal, P.; Heinz, G.; Mart´ınez, G.; Royo, P. Inorg. Chim. Acta 2003, 345,
15. (f) Galakhov, M. V.; Heinz, G.; Royo, P. Chem. Commun. 1998, 17,
and references therein.
(4) (a) Lukesˇova´, L.; Hora´cˇek, M.; Sˇteˇpnicˇka, P.; Fejfarova´, K.; Gyepes,
R.; C´ısaˇrova´, I.; Kubisˇta, J.; Mach, K. J. Organomet. Chem. 2004, 689,
1919. (b) Okuda, J.; du Plooy, K. E.; Toscano, P. J. J. Organomet. Chem.
1995, 495, 195. (c) Okuda, J.; Zimmermann, K. H.; Herdtweck, E. Angew.
Chem., Int. Ed. Engl. 1991, 30, 430. (d) Okuda, J.; Zimmermann, K. H. J.
Organomet. Chem. 1988, 344, C1. (e) Do¨tz, K. H.; Rott, J. J. Organomet.
Chem. 1988, 388, C11. (f) Macomber, D. W.; Rausch, M. D.; Jayaraman,
T. V.; Priester, R. D.; Pittman, C. U., Jr. J. Organomet. Chem. 1981, 205,
353.
(5) (a) Cuenca, T.; Royo, P. Coord. Chem. ReV. 1999, 447, 193-195.
(b) Lukesˇova´, L.; Sˇteˇpnicˇka, P.; Gyepes, R.; C´ısaˇrova´ Hora´cˇek, M. I.;
Kubisˇta, J.; Mach, K. Organometallics 2002, 21, 2639.
(6) (a) Lai, C.-H.; Cheng, C.-H.; Chou, W.-C.; Wang, S.-L. Organome-
tallics 1993, 12, 3418, and references therein. (b) Leadbeater, N. E.; Sharp,
E. L. Organometallics 2003, 22, 4167.
(7) (a) Rodrigues, C. W.; Antelmann, B.; Limberg, C.; Kaifer, E.;
Pritzkow, H. Organometallics 2001, 20, 1825. (b) Krafft, M. E.; Procter,
M. J.; Abboud, K. A. Organometallics 1999, 18, 1122.
* Corresponding author. E-mail: eva.royo@uah.es.
(1) For reviews of this topic see: (a) Butenscho¨n, H. Chem. ReV. 2000,
100, 1527. (b) Siemeling, U. Chem. ReV. 2000, 100, 1495. (c) Jutzi, P.;
Redeker, T. Eur. J. Inorg. Chem. 1998, 663. (d) Trost, B. M.; Vidal, B.;
Thommen, M. Chem.-Eur. J. 1999, 5, 1055.
(2) (a) Staal, O. K. B.; Beetstra, D. J.; Jekel, A. P.; Hessen, B.; Teuben,
J. H.; Sˇteˇpnicˇka, P.; Gyepes, R.; Hora´cˇek, M.; Pinkas, J.; Mach, K. Collect.
Czech. Chem. Commun. 2003, 68, 1119. (b) Huang, J.; Wu, T.; Qian, Y.
Chem. Commun. 2003, 2816. (c) Yong, L.; Tao, X.; Qian, F.; Qian, Y. J.
Mol. Catal. A: Chem. 2002, 184, 147. (d) Dekers, P. J. W.; Hessen, B.;
Teuben, J. H. Organometallics 2002, 21, 5122.
10.1021/om700293a CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/14/2007

3832 Organometallics, Vol. 26, No. 15, 2007
Royo et al.
Scheme 1
applications.9 Here we report the synthesis, characterization, and
chemical behavior of new hydrido tricarbonyl allyl-dimethyl-
silyl-η5-cyclopentadienyl molybdenum and tungsten derivatives.
The geometry of the tungsten compound 8a (Figure 1)
consists of a distorted tetragonal pyramid based on the three C
atoms of the carbonyl groups and one hydride ligand, the
angles around the tungsten atom C30-W-H1, C20-W-H1,
C20-W-C10, and C10-W-C30 being 75.6(5)°, 74.7(3)°,
81.8(5)°, and 80.8(4)°, respectively. The fifth coordination
position is occupied by a cyclopentadienyl ring that is essen-
tially planar, with W(1)-CCp distances that lie in the range
2.311(8)-2.394(8) Å. The silyl pendant unit shows a high dis-
order, which hinders a precise determination of the C(7)-C(8)
and C(7)-C(6) bond distances. The W-CCO bonds are within
the range for this kind of groups, and as it has been pre-
viously observed in similar compounds,14 the carbonyl trans to
the hydride ligand displays the largest W-C bond length
(W(1)-C(10) 1.996(8) Å) of the three.
Results and Discussion
Hydrido Complexes. Isolation of the target derivatives was
carried out by the typical procedure9a,b used to synthesize
cyclopentadienyl group 6 metal compounds based on the
hydrogen transfer from the cyclopentadiene to the metal
carbonyl species [M(CO)3(NCMe)3] (M ) Mo (1), W (2)). As
shown in Scheme 1, treatment of the allylsilylcyclopentadienes
3 and 4 with equimolar amounts of 1 or 2 in THF at mild
temperatures gave the cyclopentadienyl derivatives [MH{η5-
C5R4Si(CH3)2(CH2CHdCH2)}(CO)3] (M ) Mo, R ) H (5a),
R ) CH3 (6), M ) W, R ) H (7a), R ) CH3 (8a)), respectively,
which were isolated as oils in ca. 70% yield and fully
characterized by 1H and 13C NMR, IR, and elemental analysis.
Compared with the typical reaction conditions used to prepare
these hydrido cyclopentadienyl group 6 compounds, no refluxing
conditions were needed when THF was used as solvent. A
probable reason for the milder temperature conditions required
in this solvent is the formation of carbonyl molybdenum THF
adducts of general formula [Mo(CO)3(NCMe)3-n(THF)n], with
n ) 1-3, which exist in equilibrium when compound 1 or 2 is
dissolved in THF.10 Noteworthy, this synthetic approach seems
to be suitable for a variety of substituted cyclopentadienyl
systems.11-13 Crystals suitable for diffraction structure deter-
mination could be obtained from concentrated hexane solutions
of 8a.
Allyl to Prop-1-en-1-yl Isomerization. During the synthetic
studies, we found that, under certain reaction conditions, the
isomerization of the allyl pendant group took place. For
molybdenum, stirring THF solutions of 1 and the cyclopenta-
diene ligand 3 at room temperature for more than 4 h and
subsequent solvent evaporation gave oily residues with 1H NMR
spectra that showed, together with the resonances due to 5a, a
new set of signals that could be assigned to the methyl-vinyl
isomer [MoH{η5-C5H4Si(CH3)2(CHdCHCH3)}(CO)3] (5b), in
a 5a:5b ratio of ca. 2:1 (Scheme 2). Further transformations,
observed for longer periods of time, will be discussed later in
1
this article. Selected H and 13C NMR data assigned to the
olefinic pendant unit for both isomers are shown in Table 1.
For tungsten, upon heating the THF reaction mixtures,
formation of the corresponding methyl-vinyl isomers [WH{η5-
C5R4Si(CH3)2(CHdCHCH3)}(CO)3] (R ) H (7b), Me (8b)) was
(8) (a) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry; Univer-
sity Science: Mill Valley, CA, 1987. (b) Masters, C. Homogeneous
Transition-Metal Catalysis; Chapman and Hall: New York, 1981. (c)
Parshall, G. W. Homogeneous Catalysis; Wiley: New York, 1979.
(9) (a) Davis, R.; Kane-Maguire, L. A. P. In ComprehensiVe Organo-
metallic Chemistry I; Wilkinson, G. W., Stone, F. G. A., Abel, E. W., Eds.;
Elsevier: Oxford, UK, 1982; Vol. 3, Chapter 27.2, and references therein.
(b) Morris, M. J. In ComprehensiVe Organometallic Chemistry II; Abel, E.
W., Stone, F. G. A., Wilkinson, G. W., Eds.; Elsevier: Oxford, UK, 1995;
Vol. 5, Chapter 7. (c) Tamm, M.; Baker, R. J. In ComprehensiVe
Organometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.;
Elsevier: Oxford, UK, 2007; Vol. 5, Chapter 5.06.
1
detected by H NMR spectroscopy. After ca. 12 h at 45 or 70
(10) Nolan, S. P.; Lo´pez de la Vega, R.; Hoff, C. D. Organometallics
1986, 5, 2529.
(11) For comparison with some results described later on this article,
we prepared the molybdenum compounds MoH(C5HMe4)(CO)3 (16) and
MoH(C5H4SiMe3)(CO)3 (17) following the same procedure as that used
for synthesis of hydrido derivatives 5a-8a; see Experimental Section. To
the best of our knowledge, neither compound 16 nor 17 had been isolated
before (see refs 12 and 13).
(12) For related tetramethylcyclopentadienyl molybdenum compounds
see: Zhao, J.; Santos, A. M.; Herdtweck, E.; Ku¨hn, F. E. J. Mol. Catal. A:
Chem. 2004, 222, 265.
(13) For related trimethylsilylcyclopentadienyl molybdenum compounds
see: (a) Keppie, S. A.; Lappert, M. F. J. Organomet. Chem. 1969, 19, P5,
and references therein. (b) Kraihanzel, C. S.; Conville, J. J. Organomet.
Chem. 1970, 23, 357. (c) Abel, E. W.; Moorhouse, S. J. Organomet. Chem.
1971, 28, 211. (d) Malisch, W.; Schmidbaur, H.; Kuhn, M. Angew. Chem.
1972, 11, 538. (e) Heck, J.; Kriebisch, K. A.; Mellinghoff, H. Chem. Ber.
1988, 121, 1753. (f) Smith, J. M.; White, D.; Coville, N. J. Bull. Chem.
Soc. Ethiop. 1996, 10, 1.
Figure 1. Molecular diagram of complex [WH{η5-C5H4Si-
(CH3)2(CH2CHdCH2)}(CO)3] (8a). Thermal ellipsoids are shown
at 20% probability.

Cyclopentadienyl Group 6 Metal Compounds
Organometallics, Vol. 26, No. 15, 2007 3833
Scheme 2
1
Table 1. Selected H and 13C NMR Shifts (δ in ppm) of Compounds 5a-b, 7a-b, and 8a-b
Si-CH2
dCH
dCH2
Si-CHd
dCH
-CH3
5a
7a
8a
1.45 (d)
5.61 (m)
4.83, 4.87 (both d)
114.1
5b
7b
8b
5.97 (dd)
5.62 (m)
1.66 (dd)
24.6
1.43 (d)
134.0
5.58 (m)
128.3
5.96 (dd)
144.6
5.60 (m)
22.5
1.66 (dd)
4.83, 4.87 (both d)
114.3
24.5
1.66 (d)
25.3
133.9
5.69 (m)
134.4
128.8
6.04 (dd)
130.9
145.5
6.07 (m)
144.3
22.4
1.68 (dd)
22.5
4.89-4.84 (m)a
114.2
a Unresolved signals.
Scheme 3
°C, 7a:7b and 8a:8b ratios of ca. 2:1 and 1:1, respectively, were
reached, which then remained constant even after one week at
these temperatures. Complete transformation of the allyl isomers
into methyl-vinyl isomers was never observed. The same results
were observed from monitoring THF-d8 solutions of pure 5a,
7a, or 8a by 1H NMR. As the scale of the reaction was
decreased, the time for allyl isomerization was also decreased
to ca. 2 h for derivative 5a and ca. 8 h for the corresponding
tungsten species but yielded compounds 5a, 5b, 7a, 7b, and
8a, 8b, respectively, in the final equilibrium isomer ratio as
before.
Some examples of octahedral carbonyl group 6 metal
compounds with bidentate nitrogen ligands have been reported
to be active in alkene isomerization.6a In general, the studies of
olefin isomerization catalysis in recent decades identified two
major families of catalysts, which function by two different
reaction mechanisms.15 The largest family is that of transition
metal hydrides, which catalyze CdC bond migration by
addition-elimination reactions of an M-H bond. For 18-
electron carbonyl derivatives, the process requires a previous
dissociation of one CO ligand and subsequent coordination of
the olefinic moiety. Migratory insertion can occur in either of
the two ways, A or B, shown in Scheme 3. Addition of the
M-H bond to the alkene pendant unit to form the species
3-(dimethylsilylcyclopentadienyl)propyl (A-1) is a nonproduc-
tive side reaction (path A), and only addition to give the transient
species 1-methyl-2-(dimethylsilylcyclopentadienyl)ethyl (B-1)
opens access to the allyl isomerization (path B). Subsequent
â-hydrogen elimination from the silyl-methylene group of B-1
would produce selectively the observed trans-prop-1-en-1-yl
pendant unit present in isomers 5b, 7b, and 8b. Selectivity to
the trans-isomer formation is a consequence of the required
spatial position of the four atoms involved in the addition step
of the M-H bond to the alkene, due to the geometry imposed
by the chelating character of the cyclopentadienyl-alkene ligand.
It should be emphasized that, whatever the mechanism, olefin
isomerization is a kinetic phenomenon, and even with some of
the more active catalysts, equilibrium mixtures of olefins are
formed.
In order to prove the formation of the transient species
[MH{η5-C5H4Si(CH3)2(CH2-η2-CHdCH2)}(CO)2] with the
alkene coordinated to the metal center, compounds 5a and 7a
were reacted with equimolar amounts of trimethylamine N-
oxide, a reagent commonly used to favor elimination of carbonyl
ligands from carbonyl transition metal compounds by formation
(15) (a) Herrmann, W. A.; Prinz, M. In Applied Homogeneous Catalysis
with Organometallic Compounds, 2nd ed.; Cornils, B., Herrmann, W. A.,
Eds.; Wiley-VCH: Weinheim, 2002; Vol. 3, p 1119. (b) Otsuka, S.; Tani,
K. In Transition Metals for Organic Synthesis; Beller, M., Bolm, C., Eds.;
Wiley-VCH: Weinheim, 1998; Vol. 1, p 147. (c) Herrmann, W. A. In
Applied Homogeneous Catalysis with Organometallic Compounds; Cornils,
B., Herrmann, W. A., Eds.; Wiley-VCH: Weinheim, 1996; Vol. 2, p 980.
(d) In Homogeneous Catalysis, 2nd ed.; Parshall, G. W., Ittel, S. D., Eds.;
John Wiley Sons: New York, 1992; Chapter 2.
(14) (a) Shafiq, F.; Szalda, D. J.; Creutz, C.; Bullock, R. M. Organo-
metallics 2000, 19, 824. (b) Brammer, L.; Zhao, D.; Bullock, R. M.;
McMullan, R. K. Inorg. Chem. 1993, 32, 4819.

3834 Organometallics, Vol. 26, No. 15, 2007
Royo et al.
Figure 2. Molecular diagram of complex [Mo{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]2 (9). Thermal ellipsoids are shown at 30% probability.
Scheme 4
of CO2 and subsequent elimination of NMe3.16 However, the
reactions proceed through a different pathway and afforded, at
room temperature, complete transformation of the hydrido
derivatives 5a and 7a into the dinuclear species [M{η5-
C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]2 (M ) Mo (9), W (10)),
respectively, which can be isolated as solids and fully character-
ized (Scheme 4). Formation of water and trimethylamine was
confirmed by monitoring reactions of 5a and 7a with ONMe3
in Young-valved NMR tubes. 1H NMR of the mixture in
dichloromethane-d2 or benzene-d6 showed two new singlets at
δ 1.35 (CD2Cl2) or 0.47 (C6D6) and δ 2.22 (CD2Cl2) or 2.05
(C6D6), assigned to the water and trimethylamine protons,
respectively, together with the formation of 9 and 10 and the
disappearance of the proton resonances of ONMe3,17 5a, and
7a. Red crystals of 9 suitable for a diffractometric analysis (Fig-
ure 2) could be obtained from hexane solutions of the molyb-
denum derivative kept at room temperature over 2-3 days.
hindrance of the silyl allyl substituent of the cyclopentadienyl
ring. The distribution of ligands around each metal center can
be described as a distorted tetragonal pyramid based on three
C atoms of the carbonyl groups and one molybdenum center
of the other Mo[η5-C5H4Si(CH3)2(CH2CHdCH2)](CO)3 unit,
with Mo(1)-Mo(1)′-C(16) and Mo(1)-Mo(1)′-C(18) angles
slightly smaller (71.49° and 70.36°, respectively) than those
found between carbon atoms of two carbonyl ligands mutually
cis-disposed (C(16)-Mo(1)-C(17) ) 77.2(2)° and C(16)-
Mo(1)-C(18) ) 77.2(2)°; similar values are observed in the
other molecule present in the unit cell). The fifth coordination
position is occupied by a cyclopentadienyl ring that is essentially
planar, and the Mo-CCp distances lie in the range 2.331(6)-
2.413(6) Å, the C-Mo distance between the C bearing the silyl
group and the metal being one of the shortest (2.355(5) and
2.335(6) Å). As expected, the allyl group lies on the opposite
side of the cyclopentadienyl ligand of the Mo-Mo bond, while
both the terminal C-C distance (C(2)-C(3) 1.28(1) Å) and the
C(1)-C(2) (1.514(9) Å) bond lengths agree well with the allyl
formulation.
Attempts to prepare corresponding deuterido compounds
of the type [MD{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3] (M
) Mo, W) in order to gain insight into the isomerization
mechanism were unsuccessful. Reaction of 1 or 2 with
Li[η5-C5H4Si(CH3)2(CH2CHdCH2)] affords the corresponding
Li[M{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3] (M ) Mo (11),
W (12)) derivatives (Scheme 5), which were isolated and
spectroscopically characterized. However, the addition of AcOD,
MeOD, or D2O following a general procedure to synthesize
hydrido cyclopentadienyl group 6 species9 did not afford the
desired derivatives but a mixture of different proportions,
depending on the reaction conditions, of the corresponding
The molybdenum compound 9 consists of two Mo[η5-
C5H4Si(CH3)2(CH2CHdCH2)](CO)3 units, disposed in the anti
conformation and linked by a metal-metal bond, the molecule
lying on a crystallographic inversion center. Two independent
but chemically equivalent molecules appear in the unit cell. The
Mo-Mo bond length (Mo(1)-Mo(1)′ 3.254 and Mo(2)-
Mo(2)′ 3.261 Å) agrees well with other metal-metal bond
distances found for analogous derivatives of the type [Mo(η5-
9a,b,18
C5H4R)(CO)3]2
and is slightly longer than that reported
for [Mo(η5-C5H5)(CO)3]2 (3.235 Å),18c probably due to the steric
(16) For reactions between carbonyl metal compounds and ONMe3, see
the following and references therein: (a) Van Assema, S. G. A.; de Kanter,
F. J. J.; Schakel, M.; Lammertsma, K. Organometallics 2006, 25, 5286.
(b) Mathur, P.; Bhunia, A. K.; Kumar, A.; Chatterjee, S.; Mobin, S. M.
Organometallics 2002, 21, 2215. (c) Chin, Y.; Wu, C. H.; Peng, S. M.;
Lee, G. H. Organometallics 1991, 10, 1676. (d) Johnson, B. F. G.; Lewis,
J.; Pippard, D. A. J. Chem. Soc., Dalton Trans. 1981, 407.
(18) (a) Lin, G.; Wong, W.-T. J. Organomet. Chem. 1996, 522, 271. (b)
Lin, J.; Gao, P.; Li, B.; Xu, S.; Song, H.; Wang, B. Inorg. Chim. Acta
2006, 359, 4503. (c) Adams, R. D.; Collins, D. M.; Cotton, F. A. Inorg.
Chem. 1974, 13, 1086.
(17) 1H NMR data for ONMe3 (400 MHz, CD2Cl2): δ 3.29 (s, N(CH3)3).
1H NMR (400 MHz, C6D6): δ 3.17 (s, N(CH3)3).

Cyclopentadienyl Group 6 Metal Compounds
Organometallics, Vol. 26, No. 15, 2007 3835
Scheme 5
Scheme 6
Scheme 7
deuteride species [MD{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]
(M ) Mo, W) together with the desilylated compounds
[MD(η5-C5H5)(CO)3] (M ) Mo, W). Similar behavior of silyl
cyclopentadienyl group 6 lithium salts in the presence of acidic
protic media has already been observed.13e
Following a different approach, chloroform solutions of 5a
or 7a were stirred at room temperature for 8-12 h to give the
corresponding chloride species [MCl{η5-C5H4Si(CH3)2-
(CH2CHdCH2)}(CO)3] (M ) Mo (13), W (14)) with yields of
ca. 80-90%, which were isolated as red solids and fully char-
acterized. Unfortunately, treatment of these chloride mono-
cyclopentadienyl compounds with LiD, NaBD4, LiAlD4, or
LiBEt3D gave product mixtures with H NMR spectra that
indicated reduction of the CdC double bond of the allyl pendant
unit.
Dehydrogenation and Desilylation Reactions. When THF
solutions of 1 and the cyclopentadiene 3 were stirred at room
temperature for ca. 8-10 h, in addition to the mixture of isomers
5a and 5b, another two sets of signals appeared and allowed
their assignment to the dinuclear compound 9 and the unsub-
stituted cyclopentadienyl compound [MoH(η5-C5H5)(CO)3]
(15),19a,20 product of a Si-C cleavage process, in a 5a:5b:9:15
ratio of ca. 5:3:1:1 (Scheme 6). After a further 5 days at room
temperature, a red solid residue formed, which was isolated in
yields of about 35% from the pale-colored solution by filtration
and was fully characterized as dinuclear compound 9. Evapora-
tion of THF from the mother liquor allowed isolation of the
pure nonsubstituted cyclopentadienyl derivative 15 as the only
organometallic compound present in solution.
Compound 6 decomposes in ca. 12 h in THF solution at room
temperature to give the corresponding desilylated compound
[MoH(η5-C5HMe4)(CO)3]11,12 (16) as the only spectroscopically
observable organometallic species.
Thermal or photoinduced dehydrogenation of group 6 deriva-
tives of general formula [MH(C5R5)(CO)3] is a very well
documented reaction. Alt et al. and others showed that the
initial step of these processes involves removal of a carbonyl
ligand with formation of highly reactive 16-electron frag-
ments of the type [MH(C5R5)(CO)2] (Scheme 7).19b-e How-
ever, while 15 undergoes complete photoinduced dehydroge-
nation in ca. 3 h to give [Mo(C5H5)(CO)3]2 as the major final
product, the analogous tungsten hydrido complex is considerably
more stable, and after ca. 5 h the extent of reaction is of about
80%.
The easier dissociation of a carbonyl ligand from the starting
molybdenum hydrido tricarbonyl compounds, as well as the
higher reactivity of the coordinatively unsaturated molybdenum
species formed compared with those of tungsten, is probably
the key to understanding the different behavior observed for
complexes 5a and 7a or 8a. Thus, dehydrogenation of derivative
5a to give 9 seems to be a competitive process with that of
isomerization, while no dehydrogenation was evident for the
more stable tungsten hydrido derivatives 7a and 8a, which need
to be heated in order to start the allyl isomerization reaction.
When THF solutions of 5a were stirred in the absence of light,
only formation of the desilylation product 15 was detected,
which confirms the photoinduced nature of the dehydrogenation
and the isomerization reaction, both closely related to the
formation of the [MoH{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)2]
species. Moreover, the overall process strongly depends on the
solvent used, probably due to stabilization of this 16-electron
transient metal species by solvent coordination,19b-e and non-
polar solvents slow down not only the dehydrogenation reaction
of 5a but also the transformation of 5a, 7a, or 8a into 5b, 7b or
1
(19) (a) King, R. B. Organomet. Synth. 1965, 1, 156. (b) Mahmoud, K.
A.; Rest, A. J.; Alt, H. G. J. Chem. Soc., Dalton Trans. 1984, 187. (c)
Kubas, G. J.; Wasserman, H. J.; Ryan, R. R. Organometallics 1985, 4, 2012.
(d) Sweany, R. L. J. Am. Chem. Soc. 1986, 108, 6986. (e) Alt, H. G. J.;
Mahmoud, K. A.; Rest, A. J. Angew. Chem., Int. Ed. Engl. 1983, 22, 544.
(20) Structural data for 15: IR (THF): ν(CO) 2021, 1929 cm-1; ν(Mo-
1
H) 1848 cm-1. H NMR (400 MHz, C6D6): δ 4.53 (s, 5H, C5H5), -5.49
(s, 1H, Mo-H).

3836 Organometallics, Vol. 26, No. 15, 2007
Royo et al.
1
Table 2. Selected H and 13C NMR Shifts (δ in ppm) of
Scheme 8
Compounds 18 and 19
Si-CH2
18 2.08, 2.43 (both dd, 1H) 6.36 (m, 1H) 3.69, 4.03 (both d, 1H)
29.3 98.0 61.0
19 2.06, 2.84 (both dd, 1H) 5.95 (m, 1H) 3.61, 3.94 (both d, 1H)
29.7 97.7 56.8
dCH
dCH2
derivatives 5a and 7a. Disappearance of the C2 symmetry
reflected by the nonequivalence of the four cyclopentadienyl
protons, the two silicon-methyl groups, and both silicon-
methylene protons confirmed the coordination of the olefinic
moiety to the metal center. The most notable spectroscopic
features are those signals related with the pendant allyl system.
The alkene-metal interaction in compounds 18 and 19 was
evidenced by the shift of the resonances assigned to dCH and
dCH2 protons, as shown in Table 2. Similar displacements were
observed in the 13C NMR spectra, where the signals assigned
to the olefinic carbons in compounds 18 and 19 are shifted to
high field compared with those found for 5a and 7a derivatives,
as expected for a higher sp3 character of both carbon atoms,
consistent with a η2-olefin-M interaction. The values agree well
with those reported for related group 6 organometallic com-
plexes.6,7 Thus, for [Mo(η5-C5H5)Cl(CO){PPh2(C6H4-η2-CHd
CHCH3)}],7a resonances in the 13C NMR spectrum (dichlo-
romethane-d2) at δ 90.44 and 66.0 are assigned to dCH and
dCHCH3 carbon atoms, respectively, of the olefin coordinated
to the metal center. Analogous chelate coordination of allyl-
dimethylsilyl-η5-cyclopentadienyl ligands is known only for
group 4 and 5 transition metals. However, depending on the
nature of the metal center, the M-olefin bonding situation
reflects important differences. For [Zr(η5-C5H5)(η5-C5H4Si-
(CH3)2(CH2-η2-CHdCH2)(Bz)][B(C6F5)4], the shift of the sig-
nals due to the olefinic carbon atoms compared with those values
observed for the noncoordinated olefin of the analogous
zirconium neutral derivative (δ 173.1 and 91.8 for dCH and
dCH2 units, respectively, versus δ 134.9 and 110.0 for the
sp2 carbon atoms of the neutral compound [Zr(η5-C5H5)(η5-
C5H4Si(CH3)2(CH2CHdCH2)(Bz)2]) is consistent with a situ-
ation similar to that reported for classical allyl cations with a
delocalized electron density in the Zr-C-C system, with a high
polarization of the olefin system.3e,f In contrast, 13C NMR
resonances (benzene-d6) at δ 42.2 and 38.1 of the alkene pendant
unit in derivative [Nb(η5-C5H5)(η5-C5H4Si(CH3)2(CH2-η2-
CHdCH2)(Bz)] were assigned to dCH and dCH2 groups, in
accord with a well-known metallacyclopropane character re-
ported for this type of species.3d
8b, respectively, which proceeds only to a ca. 5-10% extent
in the course of 1 week in benzene-d6 solution under the same
temperature conditions used for THF solutions.
Desilylation processes of silyl-substituted cyclopentadienyl
transition metal derivatives have already been observed.5b,13 For
group 6 metal species, it has been argued that Si-C cleavage
takes place through intermediate species with M-SiR3 bonds,
which are remarkably unstable in the presence of polar solvents
and decompose to give dinuclear derivatives by M-M bond
formation.13 Reaction of the ansa-Me2Si(C5H5)2 cyclopentadiene
with [M(CO)3(EtCN)3] (M ) Cr, Mo) in refluxing DME
afforded [M(C5H5)(CO)3]2 (M ) Cr, Mo) as the only organo-
metallic derivative present in solution, while the same procedure
allowed synthesis of ansa-[{WH(CO)3}2{Me2Si(C5H5)2}] from
the starting [W(CO)3(EtCN)3] complex.13d In order to get a more
detailed picture of the desilylation process detected for the
molybdenum species, we investigated the composition of THF
solutions of 5a and [MoH(C5H4SiMe3)(CO)3] (17),11,13 by
GC-EI-MS. After 1 week at room temperature in the absence
of light, solutions of 5a and 17 produced 15 as the only soluble
1
and nonvolatile organometallic product, as evidenced by H
NMR, MS, and IR. Among these, C4H7OSi(CH3)2(C3H5)
(desilylation of 5a) and C4H7OSi(CH3)3 (desilylation of 17) were
identified by GC-EI-MS (see Experimental Section), which
permit the conclusion that the presence of THF plays an
important role in desilylation processes, as it has been argued
before. When THF solutions of 17 were exposed to solar light,
the hydrido compound underwent a competitive dehydrog-
enation reaction similar to that observed for 5a, affording a
mixture of 15 and the well-known dinuclear compound
[Mo(η5-C5H4SiMe3)(CO)3]2.13
Cationic Species. Reactions of the silyl-allyl complexes
5a and 7a with 1 equiv of [CPh3][B(C6F5)4] allowed us to
test the capacity of the alkene pendant unit to coordinate to the
metal center. In CD2Cl2, an immediate transformation was
observed by 1H NMR at -40 °C to give the cationic derivatives
[M(η5-C5H4Si(CH3)2(CH2-η2-CHdCH2)(CO)3][B(C6F5)4] (M )
Mo (18), W (19)) accompanied by elimination of HCPh3, which
was identified by 1H NMR for the resonance observed at δ 5.54
ppm (Scheme 8). In solution, 18 decomposes at room temper-
ature to a noncharacterized mixture of species, while the
tungsten derivative 19 remains unchanged under the same
conditions for at least 2-3 days. When the scale of the reactions
was increased, treatment of 5a or 7a with [CPh3][B(C6F5)4] in
dichloromethane at -15 °C for 30 min permitted isolation of
red, foamy solids, which were characterized as species 18 and
19, respectively, which can be stored at 0 °C for several days
without any decomposition.
Conclusions
Reaction at mild temperatures of the acetonitrile adducts 1
and 2, with various substituted cyclopentadiene systems in THF,
gives the hydrido derivatives 5a-8a, 16, and 17. The method
seems to be an entry of general use to substituted cyclopenta-
dienyl hydrido molybdenum and tungsten compounds, with the
advantage that no high temperatures are needed. Compounds
5a, 6, and 17 undergo Si-C cleavage at room temperature on
the silyl-substituted cyclopentadienyl systems both in solution
and as pure isolated oils. In the presence of light, a dehydro-
genation transformation that takes place with or without any
solvent is also detectable by NMR techniques for the molyb-
denum hydrides 5a and 17 to give compounds 9 and [Mo(η5-
C5H4SiMe3)(CO)3]2, respectively. Tungsten species are more
stable compared with those of molybdenum. The allyl unit
present in derivatives 5a, 7a, and 8a isomerizes in THF solution
1H and 13C NMR spectra of cationic compounds 18 and 19
showed important changes when compared with those of neutral

Cyclopentadienyl Group 6 Metal Compounds
Organometallics, Vol. 26, No. 15, 2007 3837
g, 1.98 mmol) and C5Me4HSi(CH3)2CH2CHdCH2 (0.38 g, 1.98
mmol). The reaction needs 6-8 h at room temperature to complete.
Derivative 6 was obtained as an orange oil, which can be stored
for weeks without decomposition at -30 °C. Yield: 0.56 g (71%).
Anal. Calcd for C17O3H24MoSi: C, 50.99; H, 6.05. Found: C,
to give the methyl-vinyl system of compounds 5b, 7b, and 8b,
respectively. The presumed intermediate species of the isomer-
ization are dicarbonyl hydrido compounds with the alkene unit
coordinated to the metal. Unfortunately, attempts to detect or
to isolate these through alternative synthetic procedures were
unsuccessful, but the capability of the metal centers to η2-
coordinate the olefin pendant unit was proved in the cationic
species 18 and 19.
51.32; H, 6.15. IR (THF): ν(CO) 2010, 1922 cm-1. 1H NMR (plus
trans
COSY plus HMQC, 400 MHz, C6D6): δ 5.72 (m, 1H,
J
)
HH
cis
3
cis
15.0,
J
) 8.0, JHH ) 8.4, dCH), 4.94 (d, 1H,
J
) 8.0,
HH
HH
trans
dCH2), 4.93 (d, 1H,
J
) 15.0, dCH2), 1.80, 1.68 (both s,
HH
3
each 6H, C5(CH3)4), 1.61 (d, 2H, JHH ) 8.4, Si-CH2), 0.32 (s,
6H, Si(CH3)2), -5.14 (s, 1H, Mo-H). 13C APT NMR (plus HMQC,
100 MHz, C6D6): δ 229.7 (-, CO), 134.4 (+, dCH), 113.8 (-,
dCH2), 111.0, 111.9, 91.7 (all -, SiC5(CH3)4), 25.3 (-, Si-CH2),
13.6, 11.0 (both +, C5(CH3)4), 0.1 (+, Si(CH3)2).
Experimental Section
General Information. All manipulations were performed at an
argon/vacuum manifold using standard Schlenk techniques or in
an MBraun MOD system glovebox. Solvents were dried by known
procedures and used freshly distilled. [M(NCMe)3(CO)3] (M )
Mo (1), W (2))21 were prepared according to previous reports.
The corresponding lithium salt of the cyclopentadienyl ligand,
Li[C5H5Si(CH3)2(CH2CHdCH2)], was prepared by addition of
n-BuLi to diethyl ether solutions of the cyclopentadiene system
and subsequent precipitation in hexane, according to a modified
procedure of previously reported synthesis.3e,f,22 NMR spectra were
Preparation of [WH{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]
(7a). THF (5 mL) was added to a dry mixture of 2 (1.0 g, 2.56
mmol) and C5H5Si(CH3)2CH2CHdCH2 (0.42 g, 2.56 mmol).
Stirring the reaction mixture for 8 h at room temperature gave an
orange suspension. The solvent was removed under vacuum, and
hexane (2 × 3 mL) was then added to the solid residue, the resulting
suspension was filtered, and the yellow solution was dried under
vacuum to give an orange oil. Yield: 0.81 g (72%). Anal. Calcd
for C13O3H16WSi: C, 36.12; H, 3.74. Found: C, 36.24; H, 3.98.
1
recorded in a Bruker 400 Ultrashield. H and 13C{1H} chemical
shifts are reported relative to tetramethylsilane. Coupling constants
J are given in hertz.
1
IR (THF): ν (CO) 2017, 1922 cm-1. H NMR (plus COSY plus
HMQC, 400 MHz, C6D6): δ 5.58 (m, 1H, transJHH ) 16.8, cisJHH
)
Preparation of [MoH{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]
(5a). THF (5 mL) was added to a dry mixture of 1 (0.5 g, 1.65
mmol) and C5H5Si(CH3)2CH2CHdCH2 (0.30 g, 1.81 mmol).
Stirring the reaction mixture for 15 min at room temperature gave
an orange suspension. The solvent was removed under vacuum,
and hexane (2 × 3 mL) was then added to the solid residue, the
resulting suspension was filtered, and the orange solution was dried
under vacuum to give a red oil. Yield: 0.37 g (65%). Anal. Calcd
for C13O3H16MoSi: C, 45.35; H, 4.69. Found: C, 45.51; H, 4.37.
3
cis
9.9, JHH ) 7.8, dCH), 4.87 (d, 1H,
J
) 9.9, dCH2), 4.83
HH
trans
(d, 1H,
J
) 16.8, dCH2), 4.70, 4.75 (both not resolved,
HH
3
each 2H, C5H4), 1.43 (d, 2H, JHH ) 7.8, Si-CH2), 0.03 (s, 6H,
Si(CH3)2), -7.24 (s, 1H, W-H). 13C APT NMR (plus HMQC, 100
MHz, C6D6): δ 217.3 (-, CO), 133.9 (+, dCH), 114.3 (-,
dCH2), 96.9 (-, C5H4-ipso), 93.4, 92.4 (both +, C5H4), 24.2 (-,
Si-CH2), -2.5 (+, Si(CH3)2).
Heating THF solutions of 7a at 45 °C for ca. 1 day with
subsequent evaporation of the solvent gave an oily yellow residue,
which was spectroscopically characterized as a mixture of 7a and
the methyl-vinyl isomer [WH{η5-C5H4Si(CH3)2CHdCHCH3}-
(CO)3] (7b) in a 7a:7b ratio of ca. 2:1, which allowed identification
by NMR techniques the set of signals corresponding to derivative
7b: 1H NMR (plus COSY, plus HMQC, 400 MHz, C6D6): δ 5.97
(dq, 1H, transJHH ) 18.3, 4JHH ) 1.8, dCHSi), 5.60 (dq, 1H, transJHH
) 18.3, 3JHH ) 6.3, dCHMe), 4.76 (not resolved, 4H, C5H4), 1.66
(dd, 3H, 3JHH ) 6.3, 4JHH ) 1.8, dCCH3), 0.14 (s, 6H, Si(CH3)2),
-7.21 (s, 1H, W-H). 13C APT NMR (100 MHz, C6D6,): δ 217.6
(-, CO), 144.9 (+, dCH), 128.8 (+, dCH-Si), 97.8 (+, ipso-
C5H4), 93.5, 92.5 (both +, C5H4), 22.4 (-, dCCH3), -1.6 (+,
Si(CH3)2).
1
IR (THF): ν(CO) 2020, 1930 cm-1. H NMR (plus COSY plus
HMQC, 400 MHz, C6D6): δ 5.61 (m, 1H, transJHH ) 16.8, cisJHH
)
3
cis
10.5, JHH ) 8.1, dCH), 4.87 (d, 1H,
J
) 10.5, )CH2), 4.83
HH
(d, 1H, transJHH ) 16.8, dCH2), 4.75, 4.76 (both not resolved, each
2H, C5H4), 1.45 (d, 2H, 3JHH ) 8.1, Si-CH2), 0.04 (s, 6H, SiMe2),
-5.52 (s, 1H, Mo-H). 13C APT NMR (plus HMQC, 100 MHz,
C6D6): δ 227.0 (-, CO), 134.1 (+, dCH), 114.1 (-, dCH2), 98.7
(-, ipso-C5H4), 95.5, 93.5 (both +, C5H4), 24.6 (-, Si-CH2), -2.5
(+, Si(CH3)2).
THF solutions of 5a kept at room temperature for more than 4
h and subsequent evaporation of the solvent gave an oily, red
residue, which was spectroscopically characterized as a mixture of
5a and the methyl-vinyl isomer [MoH{η5-C5H4Si(CH3)2CHd
CHCH3}(CO)3] (5b), in a 5a:5b ratio of ca. 2:1. 1H and 13C NMR
of this oil in benzene-d6 allowed assignment of the resonances due
to the methyl-vinyl isomer 5b: 1H NMR (plus COSY, plus HMQC,
Preparation of [WH{η5-C5Me4Si(CH3)2(CH2CHdCH2)}-
(CO)3] (8a). THF (5 mL) was added to a dry mixture of 2 (0.5 g,
1.28 mmol) and C5Me4HSi(CH3)2CH2CHdCH2 (0.24 g, 1.28
mmol). Stirring the reaction mixture for 12 h at 45 °C gave a dark
orange suspension. The solvent was removed under vacuum, and
hexane (2 × 3 mL) was then added to the residue. The resulting
orange-brown suspension was filtered and the solution dried under
vacuum to give a dark orange oil. Yield: 0.42 g (67%). Anal. Calcd
for C17O3H24WSi: C, 41.81; H, 4.96. Found: C, 42.30; H, 5.01.
trans
4
400 MHz, C6D6): δ 5.97 (dq, 1H,
J
) 18.3, JHH ) 1.8,
HH
dCHSi), 5.62 (dq, 1H, transJHH ) 18.3, 3JHH ) 6.0, dCHMe), 4.80
3
4
(not resolved, 4H, C5H4), 1.66 (dd, 3H, JHH ) 6.0, JHH ) 1.8,
dCCH3), 0.15 (s, 6H, Si(CH3)2), -5.49 (s, 1H, Mo-H). 13C APT
NMR (100 MHz, C6D6,): δ 227.8 (-, CO), 144.6 (+, dCH), 128.3
(+, dCH-Si), 95.6, 93.6 (both +, C5H4), 22.5 (-, dCCH3), -1.5
(+, Si(CH3)2).
1
IR (THF): ν(CO) 2007, 1914 cm-1. H NMR (plus COSY plus
Preparation of [MoH{η5-C5Me4Si(CH3)2(CH2CHdCH2)}-
(CO)3] (6). The same procedure as that used for the synthesis of
5a was followed, starting from the molybdenum compound 1 (0.6
HMQC, 400 MHz, C6D6): δ 5.69 (m, 1H, transJHH ) 16.4, cisJHH
)
3
8.8, JHH ) 7.6, dCH), 4.89-4.84 (m not resolved, 2H, dCH2),
3
1.89, 1.72 (both s, each 6H, C5(CH3)4), 1.66 (d, 2H, JHH ) 7.6,
Si-CH2), 0.30 (s, 6H, Si(CH3)2), -6.66 (s, 1H, W-H). 13C APT
NMR (plus HMQC, 100 MHz, C6D6): δ 221 (-, CO), 134.4
(+, dCH), 114.1 (-, dCH2), 110.0, 108.7, 90.5 (all -,
SiC5(CH3)4), 25.3 (-, Si-CH2), 13.8, 11.1 (both +, C5(CH3)4),
0.3 (+, Si(CH3)2).
(21) Edelmann, F.; Behrens, P.; Behrens, S.; Behrens, U. J. Organomet.
Chem. 1986, 310, 333.
(22) Spectroscopic data for Li[C5H4SiMe2(CH2CHdCH2)]: 1H NMR
(plus HMQC, 400 MHz, THF-d8): δ 5.90 (not resolved, 2H, C5H4), 5.85
(m, 1H, dCH), 5.82 (not resolved, 2H, C5H4), 4.70 (second order system,
2H, dCH2), 1.60 (dd, 1H, 3JHH ) 12, gemJHH ) 1.2, Si-CH2), 0.90 (s, 6H,
SiMe2). 13C-APT NMR (plus HMQC, 100 MHz, THF-d8): δ 137.9 (+,
dCH), 111.6 (+, C5H4), 110.9 (-, dCH2), 106.7 (+, C5H4), 106.4 (-,
C5H4-ipso), 27.1 (-, Si-CH2), -1.3 (+, SiMe2).
Heating THF solutions of 8a at 70 °C for ca. 1 day with
subsequent evaporation of the solvent gave an oily, yellow residue,
which was spectroscopically characterized as a mixture of 8a and

3838 Organometallics, Vol. 26, No. 15, 2007
Royo et al.
the methyl-vinyl isomer [WH{η5-C5Me4Si(CH3)2CHdCHCH3}-
(CO)3] (8b) in a 8a:8b ratio of ca. 1:1, which allowed identification
by NMR techniques the set of signals corresponding to derivative
8b: 1H NMR (plus COSY plus HMQC, 400 MHz, C6D6): δ 6.07
give an orange solution. The solvent was removed under vacuum
and the oily residue washed twice with hexane (2 × 3 mL) and
dried under vacuum to give a yellow foam. Yield: 0.51 g (86%).
1H NMR (plus HMQC, 400 MHz, THF-d8): δ 5.82 (m, 1H, transJHH
) 17.1, cisJHH ) 9.9, 3JHH ) 8.1, dCH), 4.77 (d, 1H, cisJHH ) 9.9,
trans
3
(dq, 1H,
J
) 18.4, JHH ) 6.4, dCH(Me)), 6.04 (dq, 1H,
HH
4
trans
trans
dCH2), 4.72 (d, 1H,
J
) 17.1, dCH2), 5.07 (not re-
J
) 18.4, JHH ) 1.2, SiCHd), 1.94, 1.74 (both s, each 6H,
HH
HH
solved, 4H, C5H4), 1.65 (d, 2H, 3JHH ) 8.1, Si-CH2), 0.12 (s, 6H,
Si(CH3)2). 13C APT NMR (plus HMQC, 100 MHz, C6D6): δ 236.2
(-, CO), 137.9 (+, dCH), 112.0 (-, dCH2), 94.0, 88.9 (both +,
C5H4), 86.6 (-, C5H4-ipso), 26.8 (-, Si-CH2), -1.5 (+, Si(CH3)2).
3
4
C5(CH3)4), 1.68 (dd, 3H, JHH ) 6.4, JHH ) 1.2, dC(CH3)), 0.37
(s, 6H, Si(CH3)2), -6.63 (s, 1H, W-H). 13C APT NMR (plus
HMQC, 100 MHz, C6D6): δ 221 (-, CO), 144.3 (+, dCH(Me)),
130.9 (+, SiCd), 110.2, 108.8, 91.0 (all -, SiC5(CH3)4), 22.5 (-,
dC(CH3)), 13.7, 11.2 (both +, SiC5(CH3)4), 0.7 (+, Si(CH3)2).
Preparation of Li[W{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]
(12). The same procedure as that described for compound 11 was
followed for the synthesis of 12, starting from 2 (0.35 g, 0.90 mmol)
and Li[C5H4Si(CH3)2(CH2CHdCH2)] (0.15 g, 0.90 mmol). Com-
pound 12 was obtained as a yellow, foamy solid. Yield: 0.51 g
Preparation of [Mo{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]2
(9). Toluene (5 mL) was added to a dry mixture of 5a (0.5 g, 1.42
mmol) and trimethylamine oxide (0.10 g, 1.42 mmol). Stirring the
reaction mixture for 2 h at room temperature gave a red solution.
Solvent was removed under vacuum and the residue washed with
hexane (2 × 3 mL) and dried under vacuum to give a red solid.
The same results were obtained when dichloromethane was used
as solvent. Yield: 0.90 g (89%). Anal. Calcd for C26O6H14Mo2Si2:
C, 45.48; H, 4.40. Found: C, 44.70; H, 4.41. IR (THF): ν(CO)
1
(86%). H NMR (plus HMQC, 400 MHz, THF-d8): δ 5.92 (not
resolved, 1H, dCH2), 4.83 (not resolved, 1H, dCH), 5.11, 5.09
3
(both not resolved, each 2H, C5H4), 1.65 (d, 2H, JHH ) 8.0,
Si-CH2), 0.13 (not resolved, 6H, Si(CH3)2). 13C APT NMR (plus
HMQC, 100 MHz, C6D6): δ 227.3 (-, CO), 136.7 (+, dCH),
112.0 (-, dCH2), 92.2, 87.6 (both +, C5H4), 86.6 (-, ipso-C5H4),
26.5 (-, Si-CH2), -1.7 (+, Si(CH3)2).
1
1954, 1913 cm-1. H NMR (plus COSY plus HMQC, 400 MHz,
trans
cis
3
C6D6): δ 5.66 (m, 1H,
J
) 16.4,
J
) 10.7, JHH ) 7.8,
HH
HH
Preparation of [MoCl{η5-C5H4Si(CH3)2(CH2CHdCH2)}-
(CO)3] (13). A chloroform (5-10 mL) solution of 5a (1.0 g, 2.84
mmol) was stirred at room temperature for 8 h. Volatiles were
removed from the resulting dark red mixture, and the solid residue
was washed twice with hexane (2 × 3 mL) and dried under vacuum
to give a red powder. Yield: 0.86 g (80%). Anal. Calcd for
C13O3H15MoClSi: C, 41.23; H, 3.99. Found: C, 41.00; H, 3.86.
IR (CH2Cl2): ν(CO) 2054, 1974 cm-1. 1H NMR (plus COSY plus
dCH), 5.07, 4.92 (both not resolved, each 2H, C5H4), 4.90 (d, 1H,
cis
trans
J
) 10.7, dCH2), 4.87 (d, 1H,
J
) 16.4, dCH2), 1.55
HH
HH
(d, 2H, 3JHH ) 7.8, Si-CH2), 0.19 (s, 6H, Si(CH3)2). 13C APT NMR
(plus HMQC, 100 MHz, C6D6): δ 226.3 (-, CO), 133.8 (+,
dCH), 114.1 (-, dCH2), 99.4 (-, C5H4-ipso), 95.6, 99.5 (both +,
C5H4), 24.6 (-, Si-CH2), -2.6 (+, Si(CH3)2).
Preparation of [W{η5-C5H4Si(CH3)2(CH2CHdCH2)}(CO)3]2]
(10). An analogous procedure to that described for 9 was followed
for the synthesis of derivative 10, starting from a solution of 7a
(1.0 g, 2.29 mmol) and trimethylamineoxide (0.17 g, 2.29 mmol).
Yield: 1.72 g (75%). Anal. Calcd for C26O6H14W2Si2: C, 36.21;
H, 3.51. Found: C, 36.43; H, 3.55. IR (THF): ν(CO) 1952, 1910
trans
cis
HMQC, 400 MHz, CDCl3): δ 5.74 (m, 1H,
J
) 18.3,
J
HH
HH
3
cis
) 9.0, JHH ) 8.1, dCH), 4.89 (d, 1H,
J
) 9.0, dCH2), 4.88
HH
(d, 1H, transJHH ) 18.3, dCH2), 5.75, 5.35 (both not resolved, each
3
2H, C5H4), 1.72 (d, 2H, JHH ) 8.1, Si-CH2), 0.27 (s, 6H,
Si(CH3)2). 13C APT NMR (plus HMQC, 100 MHz, CDCl3): δ
224.0 (-, CO), 133.3(+, dCH), 114.6 (-, dCH2), 104.6, 96.5
(both +, C5H4), 24.2 (-, Si-CH2), -2.9 (+, Si(CH3)2).
cm-1. H NMR (plus COSY plus HMQC, 400 MHz, C6D6): δ
1
trans
cis
3
5.64 (m, 1H,
J
) 16.9,
J
) 10.2, JHH ) 8.1, dCH),
HH
HH
cis
5.16, 4.91 (both not resolved, each 2H, C5H4), 4.89 (d, 1H,
J
HH
) 16.8, dCH2), 4.86 (d, 1H, transJHH ) 10.2, dCH2), 1.52 (d, 2H,
3JHH ) 8.1, Si-CH2), 0.18 (s, 6H, Si(CH3)2). 13C APT NMR (plus
HMQC, 100 MHz, C6D6): δ 215.1 (-, CO), 133.9 (+, dCH),
114.4 (-, dCH2), 95.0 (-, C5H4-ipso), 99.4, 93.5 (both +, C5H4),
24.6 (-, Si-CH2), -2.6 (+, Si(CH3)2).
Preparation of [WCl{η5-C5H4Si(CH3)2CH2CHdCH2}(CO)3]
(14). An analogous procedure to that described for 13 was fol-
lowed, starting from a chloroform solution of 7a (1.0 g, 2.29 mmol),
which was stirred at room temperature for at least 16 h to com-
plete the transformation. Yield: 0.71 g (66%). Anal. Calcd for
C13O3H15WClSi: C, 33.46; H, 3.24. Found: C, 33.55; H, 3.07. IR
Desilylation Reactions of [MoH{η5-C5H4Si(CH3)2(CH2CHd
CH2)}(CO)3] (5a) and [MoH{η5-C5H4Si(CH3)3}(CO)3] (17). THF
solutions of 5a or 17 were stirred at room temperature for 1 week
or 24 h, respectively, in the absence of light. Evaporation of the
solvent gave oily, pink residues, which were washed with hexane
to afford white precipitates, which were identified in both cases
1
(CH2Cl2): ν(CO) 2046, 1952 cm-1. H NMR (plus COSY plus
trans
cis
HMQC, 400 MHz, CDCl3): δ 5.75 (m, 1H,
J
) 18.6,
J
HH
HH
3
cis
) 9.6, JHH ) 7.8, dCH), 4.90 (d, 1H,
J
) 9.6, dCH2), 4.89
HH
trans
(d, 1H,
J
) 18.6, dCH2), 5.75, 5.40 (both not re-
HH
3
solved, each 2H, C5H4), 1.74 (d, 2H, JHH ) 7.8, Si-CH2), 0.30
(s, 6H, Si(CH3)2). 13C APT NMR (plus HMQC, 100 MHz,
CDCl3): δ 230.8, 218.8 (both -, CO), 133.2 (+, dCH), 114.7
(-, dCH2), 102.7, 94.5 (both +, C5H4), 24.3 (-, Si-CH2), -2.9
(+, Si(CH3)2).
1
by H NMR and IR as MoH(η5-C5H5)(CO)3. IR (THF): ν(CO)
2021, 1929 cm-1; ν(Mo-H) 1848 cm-1 1H NMR (400 MHz,
.
C6D6): δ 4.53 (s, 5H, C5H5), -5.49 (s, 1H, Mo-H). Aliquots of
the THF solutions were also studied by GC-IE-mass spectrom-
etry. MS(GC-EI) for desilylation of 5a: 3.23 min: m/z 172 (58%,
[C9H20OSi]+), 132 (31%, [C6H16OSi]+), 41 (100%, [C3H5]+); 5.62
min: m/z 248 (24%, [MoC8H6O3]+), 164 (91%, [MoC5H5]+), 98
(71%, [Mo]+), 65 (71%, [C5H5]+). MS(GC-EI) for desilylation of
17: 5.61 min: m/z 248 (24%, [MoC8H6O3]+), 164 (91%,
[MoC5H5]+), 98 (71%, [Mo]+), 65 (71%, [C5H5]+); 10.56 min m/z
132 (33%, [C6H16OSi]+), 118 (53%, [C5H14OSi]+), 73 (100%,
[C4H8O]+), 75 (99%, [C3H10Si + H]+), 57 (40%, [C3H5O]+), 43
(90%, [C2H3O]+).
Preparation of Li[Mo{η5-C5H4Si(CH3)2(CH2CHdCH2)}-
(CO)3] (11). THF (5 mL) was added at 0 °C to a dry mixture of 1
(0.5 g, 1.65 mmol) and Li[C5H4Si(CH3)2(CH2CHdCH2)] (0.28 g,
1.65 mmol). After addition of the solvent, the mixture was stirred
15 min at this temperature and then a further 1 h at room
temperature. During this time, the reaction suspension changed to
Preparation of [MoH(η5-C5HMe4)(CO)3] (16). The same
procedure as that used for the synthesis of 5a or 6 was followed,
starting from the molybdenum compound 1 (0.5 g, 1.65 mmol) and
C5H2Me4 (0.22 g, 1.80 mmol). The reaction is completed in 2 h at
room temperature. Derivative 11 was obtained as an orange oil.
Yield: 0.38 g (68%). Anal. Calcd for C12O3H14Mo: C, 47.70; H,
4.67. Found: C, 48.12; H, 4.68. IR (THF): ν(CO) 2011, 1922 cm-1
;
ν(Mo-H) 1850 cm-1. 1H NMR (400 MHz, C6D6): δ 4.64 (s, 1H,
C5H), 1.62, 1.61 (both s, each 6H, C5(CH3)4), -5.06 (s, 1H,
Mo-H). 13C APT NMR (plus HMQC, 100 MHz, C6D6): δ 230.0
(-, CO), 104.7, 107.4, (both -, ipso-C5(CH3)4), 88.4 (+, C5H),
12.7, 11.0 (both +, C5(CH3)4).
Preparation of [MoH(η5-C5H4SiMe3)(CO)3] (17). The same
procedure as that used for the synthesis of 5a, 6, or 11 was followed,
starting from the molybdenum compound 1 (0.80 g, 2.64 mmol)

Cyclopentadienyl Group 6 Metal Compounds
Organometallics, Vol. 26, No. 15, 2007 3839
and C5H5SiMe3 (0.36 g, 2.64 mmol). The reaction needs 4-6 h at
room temperature to complete. Derivative 17 was obtained as a
pink oil, which can be stored for weeks without any decomposition
at -30 °C. In the absence of light, this oil evolves within hours at
room temperature, both pure or in solution, into a mixture of 17
and [Mo(η5-C5H4SiMe3)(CO)3]2; see ref 13.Yield: 0.62 g (73%).
Anal. Calcd for C11O3H14MoSi: C, 41.51; H, 4.43. Found: C,
monochromated Mo KR radiation (λ ) 0.71073 Å). Data collection
was performed at 200(2) K. Multiscan23 absorption correction
procedures were applied to the data. The structures were solved,
using the WINGX package,24 by direct methods (SHELXS-97) and
refined by using full-matrix least-squares against F2 (SHELXL-
97).25 In the structure of 8a some carbon atoms show positional
disorder. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms were geometrically
placed and left riding on their parent atoms. The hydride atom was
located using the Hydex routine within the WINGX package, and
41.81; H, 4.88. IR: ν(CO) 2011, 1940 cm-1; ν(Mo-H) 1890 cm-1
.
1H NMR (400 MHz, C6D6): δ 4.76, 4.73 (both m, each 2H, C5H4),
0.03 (s, 9H, Si(CH3)3), -5.51 (s, 1H, Mo-H). 13C APT NMR (plus
HMQC, 100 MHz, C6D6): δ 227.8 (-, CO), 100.6 (-, ipso-C5H4),
95.2, 93.4 (both +, C5H4), -0.25 (+, Si(CH3)2).
its position was not refined. Full-matrix least-squares refinements
2
with 253 parameters were carried out by minimizing ∑w(Fo
-
Preparation of [Mo{η5-C5H4Si(CH3)2(CH2-η2-CHdCH2)}-
(CO)3][B(C6F5)4] (18). Dichloromethane (5 mL) was added to a
dry mixture of 5a (0.25 g, 0.73 mmol) and triphenylmethylpen-
tafluorophenylboron (0.67 g, 0.73 mmol) at -30 °C, and the mixture
stirred for 30 min. Volatiles were removed from the resulting red
dark solution, and the oily residue was washed twice with cold
hexane (2 × 3 mL) and dried under vacuum to give a red powder.
Yield: 0.68 g (92%). Anal. Calcd for C37O3H15MoSiF20B: C, 43.47;
H, 1.48. Found: C, 43.60; H, 1.70. IR (CH2Cl2): ν(CO) 2070, 1984
Fc2)2 with the SHELXL-97 weighting scheme and stopped at shift/
err < 0.001. The final residual electron density maps showed no
remarkable features.
For compound 9, all non-hydrogen atoms were anisotropically
refined. Hydrogen atoms were geometrically placed and left riding
on their parent atoms. The complex crystallizes with two indepen-
dent but chemically equivalent molecules in the unit cell, for which
two independent halves of the molecules are present in the
asymmetric unit (the other half in each case being generated by
the crystallographic inversion center). Full matrix least-squares
refinements with 325 parameters were carried out by minimizing
cm-1
.
1H NMR (plus COSY plus HMQC, 400 MHz, 273 K,
CD2Cl2): δ 6.50, 6.38, 5.86, 5.50 (all s, each 1H, C5H4), 6.09 (m,
1H,
4.03 (d, 1H,
dCH2), 2.89 (dd, 1H, JHH ) 13.7, JHH ) 5.5, Si-CH2), 2.10
J
) 14.8,
J
) 8.9, JHH ) 5.5, JHH ) 10.1, dCH),
∑w(Fo - Fc2)2 with the SHELXL-97 weighting scheme and
trans
cis
3
3
2
HH
HH
trans
cis
J
) 14.8, dCH2), 3.69 (d, 1H,
J
) 8.9,
stopped at shift/err < 0.001. The final electron density maps showed
HH
HH
2
3
peaks > 1.000 near the Mo center (e Å-3).
2
3
(dd, 1H, JHH ) 13.7, JHH ) 10.0, Si-CH2), 0.68, 0.40 (both s,
each 3H, Si(CH3)2). 13C APT NMR (plus HMQC, 100 MHz, 273
K, CD2Cl2): δ 223.222 (-, cis-CO), 210.8 (-, trans-CO), 149.6,
146.5, 139.8, 137.8, 136.5, 134.6 (all -, B(C6F5)4), 115.9 (-, ipso-
C5H4), 103.9, 102.0, 89.2 (all +, C5H4), 98.0 (+, dCH), 61.0 (-,
dCH2), 29.3 (-, Si-CH2), 0.7, -4.6 (both +, Si(CH3)2). 19F NMR
(376 MHz, 273 K, CD2Cl2): δ 134.7 (o, m-C6F5), 165.5 (p-C6F5),
170.0 (o, m-C6F5).
Crystal data: C17H24O3SiW, Mw 488.30, colorless/prism (0.38
× 0.28 × 0.25 mm3), monoclinic, space group P21/n, a )
7.1721(9) Å, b ) 17.954(4) Å, c ) 15.3349(19) Å, R ) 90°, b )
96.236(13)°, γ ) 90°, V ) 1963.0(6) Å3, Z ) 4, Dcalc ) 1.652 g
cm-3, F(000) ) 952, T ) 200 K; µ ) 5.954 mm-1; 42 907
measured reflections (θ range: 3.65-27.50°), 4470 unique (Rint
)
0.0609). R1/wR (2I > 2σ(I)) ) 0.0465/0.1029 (3450 observed
reflections, I > 2σ(I)) and R1/wR2 (all data) ) 0.0682/0.1124; data/
restrains/parameters ) 4470/0/253; GoF ) 1.080. Largest peak and
hole ) 1.679 and -1.835 e Å3. C17H24O3SiW, Mw 686.56, red/
prism (0.31 × 0.30 × 0.18 mm3), triclinic, space group P1h, a )
7.5130(15) Å, b ) 12.397(3) Å, c ) 16.679(3) Å, R ) 73.33(3)°,
Preparation of [W{η5-C5H4Si(CH3)2(CH2-η2-CHdCH2)}-
(CO)3][B(C6F5)4] (19). Dichloromethane (5 mL) was added to a
dry mixture of 7a (0.40 g, 0.92 mmol) and triphenylmethylpen-
tafluorophenylboron (0.84 g, 0.92 mmol) at -30 °C, and the mixture
stirred for 15 min. The dark red solution was then allowed to warm
to room temperature and stirred for a further 1 h. Dichlorometh-
ane was evaporated under reduced pressure and the oily resi-
due washed twice with hexane (2 × 3 mL) and dried under vacuum
to give a red powder. Yield: 0.97 g (95%). Anal. Calcd for
C37O3H15WSiF20B: C, 40.03; H, 1.36. Found: C, 40.33; H, 1.42.
IR (CH2Cl2): ν(CO) 2066, 1968 cm-1. 1H NMR (plus COSY plus
HMQC, 400 MHz, 298 K, CD2Cl2): δ 6.41, 6.21, 5.80, 5.44 (all
s, each 1H, C5H4), 5.95 (m, 1H, transJHH ) 14.7, cisJHH ) 8.4, 3JHH
b ) 88.68(3)°, γ ) 87.76(3)°, V ) 2517.4(4) Å3, Z ) 2, Dcalc
)
1.536 g cm-3, F(000) ) 694, T ) 200 K; µ ) 0.959 mm-1; 29 773
measured reflections (θ range: 3.60-25°), 5173 unique (Rint
)
0.0510); R1/wR2 (I > 2σ(I)) ) 0.0528/0.1304 (3834 observed
reflections, I > 2σ(I)) and R1/wR2 (all data) ) 0.0735/0.1391; data/
restrains/parameters 5173/0/325; GOF(on F2) ) 0.995. Largest peak
and hole ) +2.738 and -0.881 e Å3 (R1 ) ∑(||Fo| - |Fc||)/Σ|Fo|;
2
2 2
2
wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo ) ]}1/2; GOF ) {∑[w(Fo
-
Fc2)2]/(n - p)}1/2).
3
trans
) 5.1, JHH ) 9.6, dCH), 3.94 (d, 1H,
J
) 14.7, dCH2),
HH
3.61 (d, 1H, cisJHH ) 8.4, dCH2), 2.84 (dd, 1H, 2JHH ) 14.4, 3JHH
) 5.1, Si-CH2), 2.06 (dd, 1H, 2JHH ) 14.4, 3JHH ) 9.3, Si-CH2),
0.63, 0.39 (both s, each 3H, Si(CH3)2). 13C APT NMR (plus HMQC,
100 MHz, 298 K, CD2Cl2): δ 208.9 (-, CO), 149.8, 146.5, 139.6,
137.9, 136.5, 134.6 (all -, B(C6F5)4), 130.7 (+, dCH), 111.2 (-,
ipso-C5H4), 102.3, 100.0, 97.7, 88.5 (all +, C5H4), 56.9 (-, dCH2),
30.0 (-, Si-CH2), 1.4, -4.4 (both +, SiMe2).). 19F NMR (376
MHz, 298 K, CD2Cl2): δ 134.7 (o, m-C6F5), 165.5 (p-C6F5), 170.0
(o, m-C6F5).
X-ray Structure Determination of Derivatives 8a and 9.
Suitable single crystals of 8a and 9 for the X-ray diffraction study
were both grown from hexane solutions. A crystal was selected,
covered with perfluorinated ether, and mounted on a Bruker-Nonius
Kappa CCD single-crystal diffractometer equipped with graphite-
Acknowledgment. Financial support from the MEC of Spain
(Project MAT2004-02614) and from the CM (Project S-0505/
PPQ/0328) is acknowledged. E.R. thanks MEC for funding
through the RYC Program.
Supporting Information Available: Tables of crystallographic
data and bond lengths and angles. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM700293A
(23) SORTAV. Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(24) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(25) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 1998.